DAVOS, Switzerland (Reuters) - Obesity, a major factor in diabetes and heart disease, imposes costs on both public and private sectors and is a drag on economic growth, but business leaders meeting in Davos can't agree on what they can or should do to address it.

The World Economic Forum has some notable past achievements in healthcare, such as galvanizing support for the fight against AIDS and the vaccination of children in poor countries, but tackling the rise in obesity promises to be a much more complicated task.

"There are huge interests involved. The question is how can we align interests? Industry sees the impact on their bottom line. They need a healthy workforce and healthy consumers," said WEF health and healthcare expert Olivier Raynaud.

The WEF estimates a cumulative $47 trillion of output might be lost in the next 20 years due to non-communicable diseases and mental health problems, with obesity to blame for 44 percent of the diabetes burden and 23 percent of heart disease costs.

One look at the list of the strategic partners of the WEF shows how many vested interests are at play - food and drink companies are blamed for feeding the crisis, while drug manufacturers profit from soaring rates of diabetes.

There are also issues of consumer choice to take into account, and the fact that companies selling calorie-dense foods often also make a range of healthier alternatives.

"We could stop selling ice cream, but people are still going to want to eat ice cream," said Paul Bulcke, chief executive of food giant Nestle, which has been investing heavily in developing healthier products, including low-fat ice cream.

Just this week, Coca-Cola, whose chief executive Muhtar Kent is one of the co-chairs of this year's Davos gathering, launched a commercial on U.S. cable television that seeks to highlight the company's efforts in fighting obesity.

As the soft drink industry faces the threat of tighter regulation, the commercial notes that Coca-Cola sells about 180 low and no-calorie drinks and reminds viewers "if you eat and drink more calories than you burn off, you'll gain weight".

TOUGHER ISSUE THAN SMOKING

The WEF will host a private meeting on "healthy living" on Saturday of key players including executives from the food, healthcare and agriculture sectors as well as health regulators and ministers, seeking to get agreement on concrete action.

"To solve the issue of tobacco, we excluded tobacco companies. But excluding food and beverage, pharmaceuticals would be a big mistake," said the WEF's Raynard.

"The second mistake would be to only blame. The third mistake would be to be too simplistic, just focusing on reducing sugar, for example."

The British government announced this week that more food and drink companies have signed up to a voluntary pledge to cut the amount of sugar and calories in their products.

That is the kind of approach favored by Nestle's Bulcke, who rejects tighter regulation: "It's not education alone, it's not diet alone. It's all that, plus healthy physical activity."

Alison Martin, a health specialist at insurer Swiss Re who is due to address a discussion on obesity with Bulcke on Saturday, said trying to fight the problem with the same kind of taxes or bans imposed on tobacco would not work.

"There is nothing inherently wrong with eating a hamburger or drinking a can of Coke as part of a balanced diet, so it's unlike smoking," she said. "That leads it to being a more difficult, thorny issue, which is clearly why we haven't been successful in tackling it to date."

Instead of focusing on counting calories, insurers like Swiss Re are developing policies aimed at encouraging healthier living by offering lower premiums, for example if clients promise to go to the gym or buy fruit and vegetables.

Khalid Al Falih, head of Saudi Aramco, the world's biggest oil producer, said the productivity of companies was already being undermined by the poor health of some employees.

"This situation is of special concern to us because we live in a region that has one of the highest rates of obesity and diabetes in the world," he said as the WEF published new data supporting the case for more investment in workplace health.

Four out of five diabetics now live in low and middle-income countries, and global sales of diabetes medicines are expected to reach $48-$53 billion by 2016, up from $39.2 billion in 2011, according to research firm IMS Health.

"ALL YOU NEED IS SHOES"

Yasuchika Hasegawa, the CEO of drugmaker Takeda, which has interests in medicines for both diabetes and obesity, said such interventions were needed, given the deep-seated nature of the appetite for sweet and fatty foods.

"It's a fundamental problem. To fix the problem you have to change behavior, but changing behavior is the most difficult thing to do," he said.

Perhaps inspired by the fact that all but the very top VIPs have to trudge through snow to reach the WEF conference center, the most popular prescription is to promote physical activity through simple measures like building more sidewalks.

"It is hard to get people to eat healthier, but we can get people to walk. All they need is shoes," said George Halvorson, head of U.S. healthcare firm Kaiser Foundation Health Plan, who spends at least 30 minutes a day on his treadmill.

Nike, another company with a clear agenda on the issue, recently commissioned a study estimating that 9 percent of all premature deaths worldwide are due to inactivity.

But Eva Jane-Llopis, WEF chronic disease expert, said government intervention - like the soda taxes so vehemently opposed by the soft drinks industry - are still needed.

"Everybody likes physical activity because it is not contentious, but it is not a silver bullet," she said.

"We need regulation to level the playing field. Everyone is going to have to do much more if we want to turn the tide, especially in middle-income countries."

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